Method of making cathode ray tube screen



lWa'rch 4, 1958 CHARLOTTE 2,825,184

METHOD OF MAKING CATHODE RAY TUBE SCREEN 2 Sheets-Sheet 1 Filed Dec. 28,1.956

INVENTOR WE M BY I (4% as.

M ATT ORNEY March 1958 H. F. CHARLOT-TE 2,825,184

METHOD OF MAKING CATHODE RAY TUBE SCREEN Filed Dec. 28, 1956 2Sheets-Sheet 2 v 1 INVE/VTDR WE W @A a M ATTORA/E Y United States PatentMETHOD OF MAKING CATHODE RAY TUBE SCREEN Hubert Frank Charlotte,Beckenham, England Application December 28, 1956, Serial No. 631,263 2Claims. (Cl. 49--81) The present invention relates to cathode ray tubescreens.

A requirement sometimes arises for a cathode ray tube having a screwwhich incorporates a row of conductors insulated from one another, eachconductor passing from one face of the screen to the other face.

It is an object of the present invention to provide a method ofproducing such a screen.

According to the present invention a method of producing a cathode raytube screen which incorporates a row of conductors insulated from oneanother and each passing from one face of the screen to the other face,comprises the steps of coating a grid of wires with finely powderedglass, bringing two glass members together edge-to-edge on oppositesides of the grid, applying heat to fuse the said edges of the two glassmembers and the powdered glass on the grid, and subsequently removingthose parts of the grid which lie outside the screen so formed.

The grid may be produced by winding wire round a former comprising apair of like rectangular frames held together in register with oneanother. The wire is soldered to the frames along the longer edges oftheir outer faces and is out between the resulting twin lines of solder.The frames are then separated to produce two grids, each of which may beused to produce a screen.

The coating of the grids with finely powdered glass may be achieved byspraying the grid with a suspension of powdered glass in distilled wateror other medium and drying, the particle size of the powdered glassbeing not more than a few microns.

After fusion, the screen is annealed and the frame removed by cuttingthe grid. The surfaces of the screen are ground flat and polished. It isthen ready for sealing into a cathode ray tube envelope.

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which Fig. 1 is an elevation of a framewith wire wound thereon,

Fig. 2 is a cross-section of the frame of Fig. 1 taken along the line22,

Fig. 3 is a cross-section corresponding to Fig. 2 with wire woundthereon,

Fig. 4 is a cross-section of the frame and winding of Fig. 2 split intotwo parts to form two grids,

Fig. 5 shows one of the grids of Fig. 5 being sprayed with a suspensionof powdered glass,

Fig. 6 shows two pieces of glass being fused to the sprayed grid of Fig.5,

Fig. 7 is a cross-section showing the grid of Fig. 6 fused to the twopieces of glass,

Fig. 8 corresponds to Fig. 7 with the grid frame removed,

Fig. 9 corresponds to Fig. 8 after grinding, and

Fig. 10 is a plan view of the finished product shown in cross-section inFig. 9.

In Fig. 1 a rectangular frame 10 has 1,000 turns of fine wire 11 woundthereon as shown.

A cross-section of the frame 10 is shown in Figure 2 and comprises twoparts 12 and 13 which are held together by means of the screws shown at14 in Fig. 1.

Fig. 3 shows the winding in position, and it will be seen that the upperedge of each part and the corresponding lower edge are bevelled so thatthe wire in passing over the top and bottom of the frame is clear of themetal of the frame except at the two outer edges.

The wire is fixed, for example by soldering, to each of these four edgesof the frame and subsequently the wire is out between each pair ofsoldered edges and the frame parts are separated as shown in Fig. 4 toprovide two grids, each grid having 1,000 wires. The wire for examplemay be of Kovar lightly oxidised and the diameter of the wire may besuch that 1,000 turns can be accommodated within a length of 10 cms.,each turn being spaced from the other.

The assembly of one grid from Fig. 4 is mounted in a suitable rotatableholder such as that shown at 15 in Fig. 5-, the holder being mounted ona spindle 16 and rotated by means of a pulley 17 and a belt 18 coupledto a driving motor not shown. With the drive applied so as to rotate theframe 13 at slow speed, for example one revolution every few seconds, asuspension of finely powdered glass is sprayed on to the grid wires bymeans of a spray 19. The glass particle size is of the order of one ortwo microns and the glass particles are suspended in distilled water.

Spraying is continued for a time adequate to ensure that the grid wiresare completely coated with the suspension of powdered glass. This isthen dried, leaving dry glass particles clinging to the grid wires.

Referring now to Fig. 6, this shows the grid arranged so as to receivetwo glass half-discs 20 and 21. These are preheated in a suitablepre-heating furnace, not shown, and brought towards the wires of thegrid from opposite sides. Two line heaters 22 and 23 are arranged belowthe line junction and heat is applied along the junction of the twohalf-discs with the grid wires to fuse the glass at the junction on thegrid wires and in the half-discs themselves to provide a seal as shownin the cross-section of Fig. 7. The frame 13 is then removed by cuttingthe grid wires as shown in Fig. 8 and the excess glass and grid wiresare ground off to provide the finished product of Fig. 9 and Fig. 10.

The temperature to which the glass half-discs is raised by thepre-heating is approximately 600 C. and the line heaters mayconveniently be of the type providing a strip flame. The disc may thenbe sealed into a metal or glass cathode ray tube envelope and the tubemay then be subjected to the normal processes of cathode ray tubeproduction. Annealing of the screen may be effected before or after thegrinding operation, or both.

I claim:

1. A method of producing a cathode ray tube screen incorporating a rowof conductors insulated from one another and each passing from one faceof the screen to the other, the method comprising the steps of coating agrid of wires with finely powdered glass, bringing two glass memberstogether edge-to-edge on opposite sides of the grid, applying heat tofuse the said edges of the two glass members and the powdered glass onthe grid, and subsequently removing those parts of the grid which lieoutside the screen so formed.

2. A method according to claim 1, wherein the grid is coated by sprayingwith a suspension of glass particles in a liquid medium and subsequentlyevaporating off the medium.

References Cited in the file of this patent UNITED STATES PATENTS2,224,214 Brown Dec. 10, 1940 2,567,415 Walsh Sept. 11, 1951 2,752,731Altosaar July 3, 1956 2,778,161 Zaphiroponlos Jan. 22, 1957

